Verbal shorthand when thrown around casually can lead to misunderstandings especially to an industry insider who takes these terms literally.
Herewith is a short explanation of some common acronyms for plastic films in plain English starting with the basic chemical building block.
The only thing common to all three is ethylene, C2H4 or ” C2″ for short in the petrochemical realm. This building block is a monomer. String them together with variations on a theme and you got the polymer ( poly vs. mono )
polyethylene. PE, PEVA and metallocene PE are all polyethylene .
Poly Vinyl Choride or PVC for short is ethylene conjoined with chloride to make Vinyl Chloride monomer H2C=CHCl. String together a bunch of these and you got POLY vinyl chloride loosely referred to as vinyl.
image credit Tangram Technology UK
This is where the similarities end. The differences in these two largest volume thermoplastics are stark.
To achieve difference in softness or stiffness, PVC needs to have what are called plasticizers added. Because of the chlorine, PVC is naturally self-extinguishing. Polyethylene PE is just compressed natural gas so it is very flammable. PVC is about 35% more dense than even the highest density of polyethylene, or HDPE #2. PVC is a “polar” molecule which makes it a natural for RF sealing. PE is inert and must be heat sealed.
Metallocene PE ( mPE ) is polyethylene made with a metallocene catalyst. It is imperative to remember metallocene is a catalyst, not a comonomer. There is a wide variation in the species. Metallocene really is the Holy grail because it allows precise molecular weight distribution. Think molecules made by cookie cutter.
We have written exensively about PEVA. This link takes you to three blog posts which explain the differences in more depth. PEVA has caught on because it is slightly polar and can be RF welded with a minimum of modification to heirloom RF welding apparatus. We can mimic the properties of PEVA with a blend of metallocenes.
If you still have questions, please contact me joellongstreth1@gmail.com 513 238 8552
